The BRG group regularly denies all "voucher" sites. With skoosh, gtahotels, hotelclub, and a few other random websites (mostly european-based from what I can tell), when you make an "internet reservation", you are "sent" an actual paper voucher that must be presented upon checkin. If you do not have the "voucher", then you can't check in. It's unclear whether you actually get a "paper voucher" mailed to you from these sites or whether you just print out your confirmation email.

The only competing website these days to regularly undercut WR is booking.com.

Hotelsatanywhere.com used to be great, but it no longer generates rates. There are weekly sales at expedia and hotels.com every Tuesday-Wednesday, so you really have to jump when you find a BRG possibility. Orbitz and travelocity still pop up from time to time, as does the traditional reservations system on priceline.com.